S-adenosylmethionine-dependent methyltransferase (SAM-MTase or AdoMet-MTase) is a conserved

protein domain In molecular biology, a protein domain is a region of a protein's Peptide, polypeptide chain that is self-stabilizing and that Protein folding, folds independently from the rest. Each domain forms a compact folded Protein tertiary structure, thre ...

and

protein superfamily A protein superfamily is the largest grouping (clade) of proteins for which common ancestry can be inferred (see homology (biology), homology). Usually this common ancestry is inferred from structural alignment and mechanistic similarity, even if n ...

. SAM-MTase

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s are methyltransferases. There are five protein families within SAM-MTase, SAM-MTases use S-adenosyl-L-methionine as a substrate for

methylation Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...

, creating the product S-adenosyl-L-homocysteine.

Structure and subgroups

All SAM-MTases contain a structurally conserved SAM-binding domain consisting of a central seven-stranded beta-sheet that is flanked by three alpha-helices per side of the sheet. A review published in 2003 divides all methyltransferases into 5 main classes based on the structure of their catalytic domain (fold): * class I: Rossmann-like α/β, the largest subgroup. * class II: TIM β/α-barrel α/β * class III: tetrapyrrole methylase α/β * class IV: SPOUT α/β * class V: SET domain all β

References

Protein families {{Chemistry-stub Protein superfamilies Protein domains